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Theory Of Evolution

.. ons of animal and plant life, favorable variations would tend to be preserved, and unfavorable ones destroyed, the result being the formation of new species. By this chance encounter than, Darwin’s theory was provided with a rationale, and the how of evolution came to supplement the why. It is important to note, that even though the crux of Darwin’s theory was inspired by Malthus, Darwin diverged from Malthus in a critical way. Darwin’s debt to Malthus lies in the borrowing of the concept of the struggle for existence.

However, in general, what Malthus was concerned about was not how the struggle for existence affected the quality of the population (i.e., he did not suggest that in the struggle for existence the strong survive and the weak perish) but simply how it limited its numbers. Indeed, Malthus’ essay was written as a rebuttal to Godwin and Condorcet, both of whom had argued that humans, under conditions of equality, were capable of infinite progress and perfection. In the essay Malthus advanced the principle of population to refute that idea. Thus, Malthus’ principle argued that human society could never progress toward perfectibility because the population inevitably tends to increase beyond the means of subsistence and is kept within the bounds of its resources only by misery, vice, and moral restraint. Malthus’ principle of population was based on the supposed differences in reproduction rates between humans (who because of their status as top dog in the animal kingdom reproduced geometrically) and animals and plants (who could only increase arithmetically, because they served mankind as a means of sustenance). Darwin by contrast, shifted the center of attention from humans to the animal and plant kingdoms, because he was impressed by their enormous natural fertility, which was kept in check only by their own limited means of sustenance.

By shifting his perspective from mankind to animals and plants Darwin revealed the basic fallacy of Malthus’ argument. For if humans increased geometrically, animals and plants must also increase at the same rate, and perhaps even more, because overall their natural rate of reproduction is higher than that of mankind. Therefore, the struggle for existence, which to Malthus meant that hardship and misery were the defining features of human life, to Darwin meant that every species was in constant change, because nature favored the fittest through the process of natural selection. Writing the Origin Three and a half years have passed since Darwin read Malthus in October 1838 before he finally sat down to write his ideas formally in May 1842. There are two main reasons for this lengthy delay. First, throughout his life Darwin suffered from ill-health , which began to get acute in 1837, and was particularly debilitating between 1838 and 1842.

Second, during this time Darwin had more pressing matters to attend to. In particular he was working on the book Coral Reefs, papers for the Geological society, and work connected with the Zoology of the voyage of the Beagle. After completing the initial first sketch of 35 pages, he set out to write a larger and more thrall sketch in 1844 (by the time he was finished the sketch numbered 230 pages). However, Darwin still proceeded to write his ideas on evolution at a leisurely pace, and not until 1856, when urged by his colleague Lyell, did he start working on his magnum opus, the Origin. By June 1858 Darwin had completed about half of the book (on a scale three to four times as large as when it was later published), when one day a nasty surprise awaited him.

On June 18, Darwin received a manuscript from the English naturalist Wallace. In the manuscript Wallace described the theory of natural selection, and asked Darwin to comment on his ideas. Darwin thought that the only honorable thing to do was to recommend the paper for publication. Fortunately, for Darwin, Lyell suggested (and Wallace and Darwin accepted) that both Wallace’s paper and extracts from Darwin’s sketch of 1844 be published simultaneously, thus establishing the rights of both to priority. Interestingly, later on at the fiftieth anniversary meeting of their joint publication, Wallace made it clear that although the idea of natural selection came to both of them independently, Darwin’s contributions outweighed his by twenty to one because Darwin had the credit of twenty years of priority and work.

The impact of the Origin Finally, by 1859 Darwin finished writing the book, and on November 24 the Origin was first published. The sales of the book exceeded everyone’s expectations (by 1876 16,000 copies were sold in England alone), and the book’s impact was felt almost immediately. In the mid nineteenth century English society where science was a popular topic of conversation, the book competed with such dinner party topics as the Italian revolution. Even those who most bitterly despised its content were quick to concede its importance. Within the scientific community the book was creating a new paradigm that threatened to disrupt the existing status-quo.

The mood of the time is illustrated by August Weismann who states: Darwin’s book fell like a bolt from the blue; it was eagerly devoured, and while it excited in the minds of the younger students delight and enthusiasm, it aroused among the older naturalists anything from cool aversion to violent opposition. The young saw in Darwin an opportunity for a new and freer philosophical universe. For instance, young biologists such as Karl Pearson, referring to the beginning of time, were rejoiced when that wretched date BC 4004, was replaced by a long vista of millions of years of development. However, the older more professional scientists, objected to Darwin’s ideas on religious grounds. Before Darwin published the Origin, science and religion existed in harmony. There was an understanding on the part of religion that evolution was discredited by science. Now that men of science were finally favorites of the church (just two centuries ago scientists such as Galileo were unfavorably perceived by the church), it seemed foolish to give up this hard won peace for just another evolutionary hypothesis.

Sexual Selection Although Darwin discussed sexual selection in the Origin, the majority of the book (and hence the primary importance) was devoted to natural selection. However, sexual selection played a far more important role in Darwin’s The Descent of Man, and Selection in Relation to Sex (henceforth referred to as the Descent), which was published on February 24, 1871. In the Descent, sexual selection assumed an equal if not greater than role for the origin of species. For Darwin sexual selection was not simply a subcategory of natural selection, but rather an alternative or complementary mechanism of evolution. In addition, sexual selection, to a larger extent than natural selection, shifts the focus of attention to one of the most significant and least appreciated aspects of Darwin’s theory: the location of the struggle for existence lies primarily within species rather than between species.

It is therefore inaccurate, from this point on, to refer to Darwin’s theory as simply evolution by natural selection (Darwin himself called the theory the principle of evolution). The primary reason why Darwin abandoned natural selection in favor of sexual selection was the fact that natural selection could not properly explain either the evolution of man from the animals or the differences between the sexes and races. The problem is that natural selection assumes that only beneficial changes get preserved in future generations, whereas in reality the races of man differ from each other and from their nearest allies amongst the animals , in certain characters which are of no service to them in their ordinary habits of life. By contrast, sexual selection does not have to be useful for the purpose of adaptation to the environment, and it may actually work against natural selection. Therefore, Darwin now argued that any features which are not adaptive to the individual, and thus could not have been acquired through the process of natural selection, must have been acquired through sexual selection.

The Reaction to the Descent When the Descent was published in 1871 it became an immediate best-seller. The initial 2500 copies were sold almost instantaneously, and an additional 5000 copies were sold by the end of the year. The book was exceedingly controversial at the time, dealing with perhaps the most provocative evolutionary topic of all, the origin of man. In the book Darwin suggested that man differed from animals in degree and not kind, and than proceeded to conclude that man descended from a hairy, tailed quadruped, probably arboreal in its habits. Surprisingly, the reaction to the book was not as violent as one might have expected it to be, from Darwin’s previous experience with the Origin. For instance, Hooker, who at that time found evolution discussed everywhere relates the following: I dined out three times last weak, and at every table heard evolution talked of as an accepted fact, and the descent of man with calmness. However, the picture painted by Hooker is rather deceptive, as the portrayed amiability was often a matter of tone rather than of substance.

People may not have been outraged, but neither were they placated. Most of the critics choose to ridicule Darwin’s ideas rather than attack them head on. For example, a typical response, published in the Athenaeum, went along the lines of: No man will ever develop religion out of a dog or Christianity out of a cat. Nevertheless, criticism was mostly tempered with praise. A good example of this is provided in the Edinburgh Review which carefully balanced displeasure with tribute: Mr. Darwin appears to us to be not more remarkable for the acuteness and ingenuity of his powers of observation of natural phenomena, than he is for the want of logical power and sound reasoning on philosophical questions.

Therefore, while despised by some and adored by others Darwin’s ideas were quickly permeating into the fabric of society. Darwin left us a legacy which is greater than just the sum of his scientific work. Not only did his theory of evolution illuminate our past, but also the present and the future were now possible to interpret in Darwinian terms. Probably more so than any other scientific theory, Darwin’s theory of evolution, lends itself to various social interpretations known as social Darwinism. From the radical left to the radical right, Darwin’s theory has been adopted by such people as Marx and Hitler, each of whom saw in it evidence for their own ideology. Alongside the likes of Copernicus, Galileo, and Newton, Darwin has rightly earned his place in history as one of the giants of the scientific revolution.